Fiberless, Multi-Channel fNIRS-EEG System Based on Silicon Photomultipliers: Towards Sensitive and Ecological Mapping of Brain Activity and Neurovascular Coupling

Abstract

Portable neuroimaging technologies can be employed for long-term monitoring of neurophysiological and neuropathological states. Functional Near-Infrared Spectroscopy (fNIRS) and Electroencephalography (EEG) are highly suited for such a purpose. Their multimodal integration allows the evaluation of hemodynamic and electrical brain activity together with neurovascular coupling. An innovative fNIRS-EEG system is here presented. The system integrated a novel continuous-wave fNIRS component and a modified commercial EEG device. fNIRS probing relied on fiberless technology based on light emitting diodes and silicon photomultipliers (SiPMs). SiPMs are sensitive semiconductor detectors, whose large detection area maximizes photon harvesting from the scalp and overcomes limitations of fiberless technology. To optimize the signal-to-noise ratio and avoid fNIRS-EEG interference, a digital lock-in was implemented for fNIRS signal acquisition. A benchtop characterization of the fNIRS component showed its high performances with a noise equivalent power below 1 pW. Moreover, the fNIRS-EEG device was tested in vivo during tasks stimulating visual, motor and pre-frontal cortices. Finally, the capabilities to perform ecological recordings were assessed in clinical settings on one Alzheimer’s Disease patient during long-lasting cognitive tests. The system can pave the way to portable technologies for accurate evaluation of multimodal brain activity, allowing their extensive employment in ecological environments and clinical practice.

Working Memory Decline in Alzheimer’s Disease Is Detected by Complexity Analysis of Multimodal EEG-fNIRS

“…This technique is portable, relatively cheap, lightweight, and resilient to motion artifacts [ 19 ], thus being suitable for ecological measurements during the administration of clinical tests. These two scalp-located techniques could be used concurrently, providing a multimodal neuroimaging tool that is able to measure the electrical and associated hemodynamic brain activity [ 20 ]. Multimodal EEG-fNIRS has been already utilized to assess cortical connectivity alterations associated with AD [ 21 ] and to perform a data-driven identification of AD, obtaining superior performances with respect to those obtained with standalone systems [ 22 ].…”

Inquiry-based environments for bio-signal processing training in engineering education

“…Details about the Astonish experimental set-up can be found in literature. 34,35 The phases and the results of the IO learning activity. The Hemodynamic Response Function (HRF) is the most interesting component contained in the f-NIRS signal.…”

Wearable, Integrated EEG–fNIRS Technologies: A Review

“…From a technical standpoint, multimodal EEG–fNIRS is commonly achieved via mechanically combining discrete, off-the-shelf EEG and fibre-based fNIRS systems [ 10 , 11 , 12 , 13 , 14 , 17 , 18 , 28 , 29 , 30 ]. The combination of two discrete systems poses several significant challenges: (1) the mechanical challenge of coupling the necessary EEG electrodes and fNIRS sources and detectors to the head of the subject; (2) the challenge of achieving sufficient timing precision and synchronization of simultaneous fNIRS and EEG recordings; (3) the potential for electrical crosstalk between the two systems; and (4) determining which commercial fNIRS and EEG systems can be combined.…”

“…Nonintegrated EEG–fNIRS systems require an external mechanism to time-lock the acquired signals [ 28 ]. Time-locking signals consists of labelling the acquired data with marker signals or flags, and recorded signals from separate modalities are synchronized offline according to those markers.…”